Oxidation and reduction process and apparatus therefor



Y c. LIHVAICHER. OXIDATjON A/ND REDUCTION PROCESSAND APPRATUSfTHEREFOR'.

f APPLICATION mep )104.211, 1920; y 1 ,$397,562. Patented Nov.l 22,11921.

111 'HM i www' lof cells :2 as through a pipe 3.

UNITED STATES PATENT OFFICE.

CHARLES J. THATCHER, OF NEW YORK, N. Y.

OXIDATION AND REDUCTION PROCESS AND APPARATUS THEREFOR.

Application filed January 24, 1920.

To n/ wlw/n iz may concern.'

Be it known'that l, (.HARLES J. THATCHER, a citizen of the nited States, and resident of 2T 'cst 95th St., New. York. in the county of 'New York and State of New York, have invented certain new and useful Improve mentsin Oxidation and ReductionProcesses and Apparatus Therefor, of which the following is a specification.

The invention relates to a process and apparatus for electrolytically oxidizing substances, such as anthracene, or for electrolvtically reducing compounds of like or similar nature. It may be applied to the ovidation or reduction of compounds which are either solid or liquid and which are either soluble or insoluble in the electrolyte used.

The apparatus for this purpose consists of a plurality of electrolytic cells connected preferably in series or series parallel, and having separated anode and cathode compartments. The cells should preferably b e of a type providing for vigorous agitation of the electrolyte and in which the agitation tends to maintain a homogeneous suspension of any suspended substance to be oxidized or reduced, and which might otherwise settle out at the bottom, or Hoat at the top. A suitable cell for this purpose is that described in my copending application for U. S. Letters Patent, Serial No. 332,228.

The accompanying drawings show, diagrainmatically, a series of such cells with suitably arranged siphons or tubes connecting the successive anode and cathode compartments.

The apparatus and process will be described as it is adapted to the electrolytic oxidation of anthracene to anthraquinone by a dilute sulfuric acid solution of sodium bichromate. To this end, the cathode compartments of the cells are fed with spent chrome liquors from a preceding oxidation, the dissolved solids of which consist mostly of sodium and chromium sulfates and little, if any, bichromate. 1f the liquors are those derived from a prior operation of this process, they may contain sulfuric acid of 'moderate concentration and may still be hot, retaining the heat derived from the electrolytic or the oxidation process.

Such liquors may be stored in a suitable vat. as the vat l; and from which the liquors are caused to iow to the cathode compartment of the first or near end cell of a series This pipe Specification of Letters Patent.

Patented Nov. 22, 1921.

serial No. 353,743.

-its passage through the series of cells 2.

The catholyte fromthe first cell is arranged to flow to the cathode compartment of the second, and so on to each succeeding cell in the series, through siphons or over-flow pipes G.

During their passage through this suc# cession of cathode compartments the spent liquors lose most of the excess sulfuric acid which they contain, and by migration of S04-ions through the diaphragms into ythe anode compartments; hydrogen, also, es'- capes from the cathodes, tending to keep the catholyte suitably stirred. Any sodium bichromate remaining in the spent liquors from the preceding oxidation is reduced to chromium and sodium sulfates during the passage' of the catholyte through the series of cathode compartments. It is important that the spent chrome liquors thus fed into the cells should contain an excess of sulfurie acid, and an excess more than sufficient to compensate the aforesaid loss of sulfuric acid from the catholyte by migration. Otherwise, the catholyte becomes neutral or alkaline before reaching the last or far end cell and chromium compounds may precipitate.

The number ofcells employed should of course be suitably selected to fit the conditions of operation` such as current-density, rapidity of flow of the liquors, etc. In such a suitably selected number of cells, by the time the catholyte reaches the last cell of the series. it has had all its bichromate reduced to chromium and sodium sulfates and has lost'most of its sulfuric acid. n this condition, and at this point, the catholyte is now allowed to flow into the anode compartment of the last cell-that farthest removed in the series from the near, end cell into which the catholyte was fed. This transference of the catholyte to the first of the anode compartments may be accomplished in any suitable manner, as by a siphon 7 or by an overiow arrangement or any other suitable means, (not shown).

The anolyte now begins to lbe oxidized at the anode of the cell, regenerating sodium bichromate. Into this or some suitably ad- :soA

jacent `anolyte compartment, anthracene is now fed'in accordance with the process, as from a tank 8, preferably in the form of a paste of a very finely-divided, sublimed anthracene `mixed up with 'a little water, or referably with a little of the catholyte 'rom the last cell Afrom which it has been suitably withdrawn for that purpose. It is advantageous to thus use catholyte, similarly to the procedure set forth in an application for U. S. Letters Patent filed by me of even date herewith, because it avoids dilution of the liquors, which since they are used over again, would be cumulative and vfinally necessitate evaporation to restore the requisite concentration.

With a suitable cell, provided with a heat insulated covering if necessary, and at a suitable current-density, the anolyte at this point will be at a temperature of 75 C. or thereabout. All of the conditions of the anolyte, therefore, closely approximate those now employed in the chemical oxidation of anthracene to anthraquinone, which, as in this anoly-te, is started at a temperature of 7 5 C. or so in a liquid free` or substantially free from sodium bichromate and sulfuric acid. ln the chemical oxidation, a dilute sulfuric acid solution of sodium bichromate .is gradually added, with const-ant stirring,

nditions found necessary in the manufac ture of anthraquinone.

By the electrolytic oxidation, sodium bichromate and sulfuric acid begin to be :formed now and the primary reaction of oxidizing the Vanthracene to anthraquinone is induced. just as in the chemical oxidation process.l Under suitably arranged conditions, the oxidation of the anthracene keeps step with` the generation of sodium bichromate in the anolyte; so that there is vat. no time any considerable excess of bichromate or sulfuric acid; excessive oxidation, resulting in formation 'of carbon dioxid and water, is thus avoided, as contrasted with previous unsuccessful attempts to oxidize anthracene in electrolytic cells.

Both the anthracene and anthraquinone are kept ina homogeneous suspension in they electrolyte by vigorous agitation such as may be provided by a stirrer of the electrolytic cell described in my aforementioned patent application. 'In this homogeneous condition, the anolyte passes through the second and so on through each successive anode compartment of the series of cells, through suitably disposed over-flow pipes or siphons 9, or by some other proper means. It is advantageous to have the inlet leg of the .be no settling out of the suspended anthracene or anthraquinone during its passage through the said siphons. And itis also advantageous to so select the bore of these siphons that a suitably rapid stream of anolyte will flow through the siphons to insure complete carrying over of suspended solids; o-r any other suitable means of accomplishing the same result may be employed.

By thetime the anolyte reaches the last of the anode compartments, the anthracene is all or substantially all oxidized to anthraquinone, the temperature conditions being so controlled that the last cell of the series approximates a temperature of 95 C. It should require ten.(10) hours. or more for the suspended anthracene to pass through the series of anode compartments during its oxidation'. From the last of this series of compartments the anolyte, bearing the suspended solids, flows through the overiow siphon 5, the height of the opening of which determines the level of the entire series of electrolytes. through the cells can be cont-rolled by a cock `10 at any suitable point, e. g. inthe Siphon` connecting the anolyte and catholyte.

The mixture flowing through the overflow siphon may be collected'if necessary in a vat 11 provided with a heating coil 12 or other heating means and with a stirrer 18, as shown, to complete the oxidation of the anthracene to any suitable degree. From the latter vat, the anthraquinone in suspension flows outto a filter or other means (not shown) for separating the anthraquinone which is to be dried, and the filtrate is returned to 4the vat 1 for a further cycle of operations.

1. The process of electrolytic oxidation or reduction, which consists in inducin a flow of spent electrolyte, exposing the e ectrolyte in the first direction of flow to electrolytic action opposed to the primary reaction, and inthe reverse direction of flow to electrolytic action inducing the primar-y reaction, introducing the substance to be converted by theV primary reaction at substantially the most -inert condition of the electrolyte, collecting the electrolyte and said ./substance, and separatingthe latter from the The rate, of flow lll tially the most inert condition of the electrolyte; collecting the electrolyte and said substance', separating the latter from the former, and returning the spent electrolyte for a further cycle.

3. The process of manufacturing anthraquinone by electrolytic oxidation of anthracene; which consists in inducing a iow of 'a electrolyte comprising an acid-reacting aqueous solution containing chromium compounds capable of being electrolytically oxidized to bichromate ions; exposing the electrolyte in the first direction of iow to electrolytic reducing action, and in the reverse direction of flow to electrolytic oxidizing action. introducing anthracene substantially at the point of reversal, causing anthracene and the anthraquinone formed to be carried along by said electrolyte and continuing the electrolysis until substantially all of the anthracene is oxidized to anthraquinone7 collecting the electrolyte, and sepa rating the anthraquinone therefrom.

4. The process of manufacturing anthraquinone by electrolytic oxidation of anthracene, which consists in inducing a flow of an electrolyte composed of acid-reacting aqueous solution containing chromium compounds capable of being electrolytically oxidized to bichromate ions; exposing the electrolyte in the first direction of flow to electrolytic reducing action, and in the reverse direction of flow to electrolytic oxidizing action, introducing anthracene suspended in a portion of reduced electrolyte substantially at the point of reversal, causing anthracene and the anthraquinone formed to be carried along by said electrolyte and continuing the electrolysis until substantially all of the anthracene is oxidized to anthraquinone, collecting the electrolyte1 and separating the anthraquinone therefrom.

5. Electrolytic oxidation or reduction apparatus, comprising: a series of electrolytic cells with separated anode and cathode compartments; means to feed electrolyte to a compartment of an end cell; connections between the successive compartments of like polarity to permit the electrolyte to flow through the series in one direction; means to maintain the liquid level within the cells; a connection between the cathode and anode compartments of the far end cell; and communications between the successive compartments of polarity opposite to said irst series to permit the electrolyte to flow in a direction reverse to its initial flow through the compartments.

6. Electrolytic oxidation or reduction apparatus; comprising: a series of electrolytic cells with separated anode and cathode compartments; means to feed electrolyte to a compartment of an end cell: connections between the successive compartments to permit the electrolyte to iow through the series in one direction; means to maintain the liquid level within the cell; a connection between the athode and anode compartments of the far end cell; communications between the successive compartments of like polarityl to permit the electrolyte to fiow in a direction reverse to its initial flow through the compartments; and means to cont-rol the flow.

7. Electrolytic oxidation or reduction apparatus, comprising: a series of electrolytic cells `with separated anode and cathode compartments; means to feed electrolyte to a' of the compartments of the far end cell the material to be reacted upon.

8. Electrolytic oxidation or reduction apparatus, comprising: a series of electrolytic cells with separated anode and cathode compartments; means to feed electrolyte to a compartment of an end cell; connections between the successive compartments to permit the electrolyte to flow through the series in onel direction; 'means to control the supply of electrolyte to maintain the liquid level within the cells; aconnection between the cathode and anode compartments of the far end cell; communications between the .Successive compartments of like polarity to permit the electrolyte to flow in a direction reverse to its initial flow through the compartments; and an outlet connection from a compartment of the near end cell adapted to determine the electrolyte level.

9. Electrolytic oxidation or reduction apparatus, comprising: a series of electrolytic cells with separated anode and cathode compartments; means to feed electrolyte to a compartment of an end cell; connections between the successive compartments to permit the electrolyte to flow through the series in one direction; means to control the supply of electrolyte to maintain the liquid level within the cells; a connection between the cathode and anode compartments of the far end cell; communications between the successive compartments of like polarity to permit the electrolyte to iiow in a direction reverse to its initial iiow through the compartments; an outlet connection from a coinpartment of the near end cell adapted to determine the electrolytelevel, and a tank to receive the flow therefrom and provided withl suitable stirring apparatus.

10. Electrolytic oxidation or reduction apparatus, comprising:l a series of electrolytic cells with separated anode and cathode conrpartrnents; a supply tank to feed electrolytel to a compartment of an end cell; connections ments of the far end cell; communicationsl between the successive compartments 'of like polarity to permit the electrolyte to iow in a direction reverse to its initial flow through the compartments; means to control the flow; means to admit to a compartment of the far end cells the material to be reacted upon; an outlet connection from a com# partrnent of the near cell adapted to determine the electrolyte level; and a suitable tank to receive the flow therefrom, and stirring apparatus for stirring the electrolyte delivered thereto.

l1. The process of electrolytic oxidation or reduction, which consists in inducing a loW of spent electrolyte, exposing the -electrolyte in the first direction of flow to electrolytic action opposed to the primary reaction, and in the reverse direction Aof flow to electrolytic action inducing the primary reaction, causing the substance to be converted by the primary reaction to enterdnto the electrolyte in lwhich the primary Vreaction occurs, collecting the'electrolyte and said substance, and separating the latter from the former.

Signed at New York, in the county of New York and State of New York, this 23rd day of January, A. D. 1920.

CHARLES i. THATCHER. 

